The Applicants' U.S. patent application No. 160804 filed Feb. 16, 1988 now U.S. Pat. No. 4,809,645 proposes a system for protecting boiler screens constituted by vertical tubes which are interconnected by welded fixing fins, disposed between refractory bricks, and provided with hooking means engaging the refractory bricks, the system being characterized in that the tubes are also provided with vertical auxiliary fins at an angle lying in the range 30.degree. to 60.degree. to the plane of the fixing fins, in that the auxiliary fins are periodically interrupted over vertical lengths of the tubes, in that a first portion of the refractory bricks are provided with vertical notches of width and thickness corresponding to the width and thickness of the auxiliary fins and extending from the bottom over only a fraction of their height, and the other portion with vertical notches extending over their entire height, and in that the bricks of the first portion are hooked onto the top portions of the auxiliary fins and the bricks of the other portion are threaded onto said auxiliary fins above the bricks of the first portion.
Such a system nevertheless requires each tube to be provided not only with junction fins, but also with fins for hooking to bricks, and the system also requires two different types of brick to be provided.
The object of the present invention is to provide a system for protecting boiler screens which does not require brick hooking fins to be welded onto each tube and which makes use of only one type of refractory brick.